1. Field of the Invention
This invention relates to a heavy duty pneumatic tire for use in heavy vehicles such as truck, bus and the like having an excellent resistance to uneven wear without increasing noise generated, and more particularly to a heavy duty pneumatic tire having a block pattern.
2. Description of Related Art
In the conventional heavy duty pneumatic tire having a block pattern, the occurrence of uneven wear called as heel and toe wear has been controlled by making a worn amount at a stepping-in side portion of the block large and a worn amount at a kicking-out side region of the block small. That is, when only one block b is schematically shown as a perspective view in FIG. 5, it has substantially a semicylindrical shape that an outer profile of the block b at a section perpendicular to a rotating axis of the tire is rendered into an arc shape having a radius of curvature smaller than an outer profile of the tire to lower each of heights at a stepping-in side S and kicking-out side R as compared with the other remaining portion of the block.
In such a conventional technique, it is recognized to improve the heel and toe wear, but when the worn amount at the kicking-out side R is observed in a widthwise direction of the block on and after the middle worn stage, it becomes larger at a side of a tread center rather than at a side of a tread end and hence it is difficult to effectively control the heel and toe wear throughout wear life of the tire. And also, there is a problem that noise is considerably deteriorated as compared with the case of tires not taking the above countermeasure for the uneven wear.
The latter is due to the fact that the stepping-in side portion of the block contacts with ground as a line before the adoption of the countermeasure for the uneven wear but contacts with ground as a plane after the adoption of the above countermeasure.